It is known to use analog display instruments with a pointer and a scale, with the measured value being indicated on the scale by means of the pointer, for example for an analog representation of the speed, the rotational speed, the engine temperature, or the fill level of the fuel storage tank. Such an analog display instrument may also be referred to as a pointing instrument or a pointer gauge.
A “scale” should be understood to comprise, e.g., a succession of a number of graduation marks on a display surface. The spacing of these graduation marks on the scale may be uniform or, if necessary, uneven. These graduation marks are used to read the currently displayed measured values, for example with the aid of a movable pointer. For this purpose, at least some of the graduation marks may be labeled with a respective value representing a physical quantity, such as a speed.
It is also known to digitally represent information by means of a suitable display for the representation of numbers, characters, and symbols. For example, numeric displays may be employed. In such displays, in addition, pictorial representations can also be provided, such as are typical, for example, when using a navigation system, a representation of the view of the surroundings, or a “back-up camera” for use in a system provided for driving in reverse.
Thus, a hybrid combination display instrument will be comprised of at least one analog display region and at least one digital display region, disposed next to each other. A combination display instrument can also be configured such that it has a digital display region in a central region, having a respective analog display region next to it laterally, in particular one analog display region on the left and one on the right.
In such a combination display instrument, a speed measurement value or a rotational speed measurement value can also be displayed, across the entire range of these values. The measured value is then displayed, for example, on a scale which is formed in part by the analog display region and in part by the digital display region.
Ordinarily, such hybrid combination display instruments are equipped with a complete “dial application”, with a scale of the measured values to be displayed, which scale is disposed under a pointer. The “dial application”, which may also be referred to as a “pointer dial”, is at least partially disposed in the digital display region of a display provided for the display of digital information. However, the area of the (digital) display which can be used to display information is thereby reduced.
In addition, the dial display structure, which must be provided with means of illumination, is clearly distinguished from the surface of the rest of the display from the visual standpoint, by its overall height, so that the analog and digital display regions are notably “separated” from each other from the visual standpoint. For reasons of optical or design considerations, automotive manufacturers are desirous of having available solutions which offer an improved transition between the analog display region and the digital display region. This is particularly relevant in cases where the display of a measured value takes place on a scale which extends over the analog and digital display regions.
DE 10 2010 055 077 A1 discloses a display device for a motor vehicle having at least one layer which is light-transmitting over at least part of its extent and is capable of displaying numbers, scales, or the like. A light guiding means for illuminating the layer is disposed behind the layer, considered in the viewing direction. In addition, the light guiding means has an essentially flat structure, and has at least one lateral surface for admission (coupling) of light. A recess is provided in the light guiding means. The light guiding means is also provided with a reflective coating on its underside, and, on its upper side, with structures for external coupling.
The underlying problem of the invention of DE 10 2010 055 077 A1 was to devise a display device for a motor vehicle, the installation height (thickness) of which display device can be kept relatively small. In order to provide a proper display which has uniformly distributed illumination intensity, a light guiding means was proposed which has an upper side facing the viewer and a lower side facing away from the viewer, which (lower side) preferably extends in a conical shape from an outer diameter toward an inner diameter. The light guiding means is [thus] designed with a cross-section which tapers radially inward. In addition, the light guiding means is thickened on its periphery, for the purpose of improving the light coupling or the light distribution within the light guiding means. For purposes of the display function, a light-transmitting region with a scale and a pointer is disposed above the light guiding means.
The document DE 10 2013 223 244 A1 discloses a device for a vehicle for displaying at least one symbol, which has a light-transmitting plastic layer with an opaque coating. A “symbol surface” for displaying of a symbol is removed (cut out or omitted) from the opaque coating. The device has an opaque intermediate component which is applied on the opaque coating, outside of and surrounding the symbol surface, which intermediate component forms a light well adjoining the symbol surface. In addition, a diffuser element is provided which is disposed in the light well, and via a gap is disposed at a distance from the symbol surface, which diffuser element is designed to convert light incident on the diffuser element into a diffuse light for illuminating the symbol surface.
DE 102 20 335 A1 discloses a display device, in particular for a motor vehicle, with a display field which has an at least optoelectronic display means, in particular a liquid crystal display, in a surrounding field. The surrounding field is formed by a luminous surface element the light intensity and color location of which when in the luminous state corresponds at least to a large degree to the light intensity and color location of the display surface of the optoelectronic display means.
The luminous surface element is designed as a flat active light source or as a flat light-guiding plate, wherewith light from one or more light sources can be applied to the narrow side of said plate.
DE 10 2009 011 948 A1 describes a vehicle instrument panel with at least one liquid crystal display of the transparent-positive type, with its rear side being illuminated by daylight coming from the direction where the driver is located. The display has information areas and neutral areas, and is supported on a transparent holder over the information regions.
Such known combinations of an analog and a digital display region in a hybrid combination display instrument, from the prior art, are often produced with a complete pointer dial applied over the display, which reduces the useful area of the display. On the other hand, the number of plastic parts needed for the display, which parts are disposed, for example, above the surface of the display, does not allow a flat and homogeneous transition between the digital and the analog display regions of the scale.